Surface codes are a key approach to achieving practical large-scale quantum computation. This article introduces the surface code, explaining its structure, error correction, and implementation. The surface code is a type of stabilizer code, derived from Kitaev's toric code, and operates on a two-dimensional array of physical qubits. It is particularly effective at tolerating local errors, with error thresholds up to 1% per operation, making it a promising candidate for fault-tolerant quantum computing. The surface code uses logical qubits, which are encoded in physical qubits through entanglement and measurement. Logical qubits can be moved and manipulated using braid transformations, which are equivalent to controlled-NOT operations. The surface code also supports single-qubit gates such as Hadamard, S, and T, which are essential for universal quantum computation. The article discusses the physical implementation of the surface code, noting that it requires a large number of physical qubits—on the order of 10^3 to 10^4 per logical qubit. For example, factoring a 2000-bit number using Shor's algorithm would require about a billion physical qubits. The surface code's error tolerance is relatively high, but it requires extensive classical control and monitoring. The surface code's error detection is based on stabilizers, which are operators that commute with each other. These stabilizers are used to measure the state of the system and detect errors. The quiescent state of the surface code is the state that results from the simultaneous measurement of all stabilizers, and it is used to store quantum information. The article also discusses the logical operators of the surface code, which are used to manipulate the logical qubits. These operators, such as X_L and Z_L, commute with the stabilizers and allow for the manipulation of the logical qubits without affecting the stabilizers. The logical operators are essential for performing quantum computations on the surface code. In conclusion, the surface code is a promising approach to achieving practical large-scale quantum computation. It is effective at tolerating local errors and requires extensive classical control and monitoring. The surface code's ability to encode logical qubits and perform quantum operations makes it a key component of future quantum computers.Surface codes are a key approach to achieving practical large-scale quantum computation. This article introduces the surface code, explaining its structure, error correction, and implementation. The surface code is a type of stabilizer code, derived from Kitaev's toric code, and operates on a two-dimensional array of physical qubits. It is particularly effective at tolerating local errors, with error thresholds up to 1% per operation, making it a promising candidate for fault-tolerant quantum computing. The surface code uses logical qubits, which are encoded in physical qubits through entanglement and measurement. Logical qubits can be moved and manipulated using braid transformations, which are equivalent to controlled-NOT operations. The surface code also supports single-qubit gates such as Hadamard, S, and T, which are essential for universal quantum computation. The article discusses the physical implementation of the surface code, noting that it requires a large number of physical qubits—on the order of 10^3 to 10^4 per logical qubit. For example, factoring a 2000-bit number using Shor's algorithm would require about a billion physical qubits. The surface code's error tolerance is relatively high, but it requires extensive classical control and monitoring. The surface code's error detection is based on stabilizers, which are operators that commute with each other. These stabilizers are used to measure the state of the system and detect errors. The quiescent state of the surface code is the state that results from the simultaneous measurement of all stabilizers, and it is used to store quantum information. The article also discusses the logical operators of the surface code, which are used to manipulate the logical qubits. These operators, such as X_L and Z_L, commute with the stabilizers and allow for the manipulation of the logical qubits without affecting the stabilizers. The logical operators are essential for performing quantum computations on the surface code. In conclusion, the surface code is a promising approach to achieving practical large-scale quantum computation. It is effective at tolerating local errors and requires extensive classical control and monitoring. The surface code's ability to encode logical qubits and perform quantum operations makes it a key component of future quantum computers.